This application relates to devices and systems for optical wavelength-division multiplexed (xe2x80x9cWDMxe2x80x9d) communication systems, and more specifically, to devices and systems for processing WDM signals.
An optical WDM system uses a single fiber link to simultaneously transmit optical carriers of different wavelengths so that different channels of data can be carried by the different carriers and sent over the optical fiber link at the same time. The optical signal in such a fiber link is a WDM signal because it is a combination of different optical carriers at different wavelengths. Hence, a WDM system can provide a broadband transmission and a high transmission speed. Dense WDM (xe2x80x9cDWDMxe2x80x9d) techniques have been used to increase the number of multiplexed wavelengths in a WDM fiber link by reducing the wavelength spacing between two adjacent wavelengths. In addition, a WDM system can be made scalable to allow expansion of the transmission capacity by simply adding the number of optical carriers in the existing fiber links without adding new fiber links.
One of the technical issues of WDM systems is the handling or processing of the WDM signals in a WDM network, including, among others, routing, switching, demultiplexing, multiplexing, adding, dropping, wavelength conversion, and regenerating. Various techniques have been developed or are under development to address these and other WDM processing issues. Some of these techniques use an xe2x80x9copaquexe2x80x9d design in which the optical WDM signals are first converted into electronic form for electronic processing and then are converted back into the optical domain for transmission. The electronic conversion allows many signal processing operations to be performed electronically by electronic circuits and devices, including switching, regenerating, buffering, monitoring the bit error rate, etc.
The opaque systems can use matured and well-established electronic technologies to provide relatively reliable operations and performance. However, the optical-electronic-optical conversion may increase the operational latency and require expensive optical-electronic converting devices. In particular, such conversion is usually data-format specific and must be designed to meet the requirements of existing protocols and data bit rates. Hence, although the converting devices can be designed to accommodate multiple existing data formats but it can be difficult, if not impossible, to adapt the converting devices to new data formats emerged in the future.
One alternative to the opaque design is a xe2x80x9ctransparentxe2x80x9d design where no optical-to-electronic conversion is performed and an optical signal is directly routed or switched in the optical domain. Many conventional transparent systems passively direct each optical carrier at a specific wavelength to a fixed port or a desired port according to a command without changing the properties of the carrier such as the carrier wavelength and the data format embedded therein. Hence, such transparent systems are xe2x80x9ctransparentxe2x80x9d to the protocols and data bit rates of different signals in different optical carriers. In addition, complex and expensive optical-electronic-optical converting devices can be eliminated to reduce the system cost, physical size, and power requirements.
The present disclosure includes hybrid opto-electronic WDM processing systems that combine features of both the opaque and transparent designs to provide scalable and versatile WDM processing capabilities. The scalability of such hybrid systems allows processing of WDM signals with variable numbers of multiplexed channels of different wavelengths and permits receiving and processing of a variable number of WDM signals, i.e., input WDM fibers. The processing functions include, among others, signal detection, signal monitoring, wavelength conversion, signal regeneration, and generation of new WDM channels. The versatile aspect of such hybrid systems allows system reconfiguration to meet different existing application requirements and adaptability to future updates and new application requirements. A reconfigurable modular WDM architecture is disclosed to achieve desired scalability and versatility for the evolving optical WDM fiber communications.
A WDM processing system according to one embodiment may include an optical switching fabric with an array of optical switching elements and a plurality of module slots surrounding the switching fabric for engaging removable processing modules to optically communicate with the switching fabric. Each removable module includes a plurality of receiving or transmitting ports that are optically linked to the respective switching elements in the switching fabric when engaged in a respective module slot. This WDM processing system is scalable because the number of inputs of each input module or the number of outputs of each output module can be expanded up to a maximum number set by the design of the switching fabric.
In one implementation, an input demux module, an output mux module, a laser module with an array of lasers of different wavelengths, and a detector array with an array of photodetectors are engaged to selected module slots. Each of the lasers may be driven by a respective output signal from a photodetector to convert a WDM wavelength or to regenerate a signal at the same wavelength. In addition, each laser may be driven by a control signal to produce a new signal with a new channel of data at a desired WDM wavelength.
In another implementation, one or more arrays of semiconductor optical amplifiers may be placed in one or more module slots. Each semiconductor optical amplifier may be designed to use the semiconductor gain medium to optically produce an optical signal. Such an optical signal may be at a WDM wavelength different from an input WDM wavelength when the wavelength conversion is desired, or an amplified version of an input optical signal when the regeneration is desired, or a new optical signal at a desired WDM wavelength in response to an electronic signal that drives the semiconductor medium. Such a semiconductor optical amplifier may substitute a laser for the wavelength conversion, signal regeneration, or generation of a new signal without converting an input optical signal into an electronic signal.